Preparation of acylated pectin with gallic acid through enzymatic method and their emulsifying properties, antioxidation activities and antibacterial activities.

In this study, native pectin (Na-Pe) was acylated with gallic acid through enzymatic method. UV-Vis, Fourier transform infrared spectroscopy and proton NMR analyses demonstrated that the phenolic hydroxyl group on gallic acid attacked the carbomethoxy of Na-Pe and replaced the methoxy group to form a new ester group under catalysis. The galloyl content of acylated pectin prepared via 24-h reaction (Ac1-Pe) was 16.8%, while that prepared via 48-h reaction (Ac2-Pe) reached 20.7%. The emulsifying properties, antioxidation activities and antibacterial activities of acylated pectin was significantly improved compared with those of Na-Pe. The emulsion activity and emulsion stability of the pectin emulsion improved from 1.08% and 56.13% (Na-Pe) to 1.57% and 88.27% (Ac1-Pe) and 1.71% and 93.3% (Ac2-Pe), respectively. The DPPH clearance of the pectin improved from 2.68% (Na-Pe) to 68.92% (Ac1-Pe) and 76.98% (Ac2-Pe) and the inhibition ratio in the β-carotene bleaching assay of the pectin increased from 3.15% (Na-Pe) to 73.02% (Ac1-Pe) and 78.96% (Ac2-Pe). The inhibition rate of the pectin against Escherichia coli and Staphylococcus aureus also improved from 2.93% and 8.92% (Na-Pe) to 26.95% and 42.18% (Ac1-Pe) and 31.56% and 47.87% (Ac2-Pe), respectively.